Light bulb question- running a 120 volt bulb at 30 volts- watts reduced by 75%?

[CalG]

I have some lightbulbs in my kitchen in a 4 bulb fixture. We've been in the house about 21 years. Those lights are the first on and last off every day. One finally burned out a few years ago. I had a hard time reading it, but I finally figured out they are 130v bulbs. They give off a nice yellow color, not harsh white. Since there's 4 of them, its plenty to light up our little two-butt kitchen.

Those "long life bulbs" are exactly the ones the EPA has banned for being so "inefficient" . Considered energy wasters as they turn most of the consumed electricity into heat instead of light.
Thanks to that attitude we now have those wonderful CFLs and the ghastly light of LEDs.
Progress!

 

[k0ua]

For a dollar, I would just screw it in. It's not going to burn up unless it is defective from the git go.

Exactly.. Just screw it in and see what happens.

 

[k0ua]

I have some lightbulbs in my kitchen in a 4 bulb fixture. We've been in the house about 21 years. Those lights are the first on and last off every day. One finally burned out a few years ago. I had a hard time reading it, but I finally figured out they are 130v bulbs. They give off a nice yellow color, not harsh white. Since there's 4 of them, its plenty to light up our little two-butt kitchen.

I noticed that many of the bulbs in our house were 130 volt bulbs also. They do last quite a bit longer, some are still original and we have been here 14 years.

 

[EddieWalker]

Will an LED light bulb work? I've seen that they will light up with far less then 120 volts. It takes a second or two, or three, for them to light up, but then they do nice and bright.

The reason I know this is that I do work in old houses and it's common for the wiring to be loose somewhere and the voltage at the light is anywhere from 30 to 60 volts. It will set off my tester like it's hot, but it's not enough to power a regular light bulb. Sometimes I've found the loose wires in a junction somewhere. Either they where taped together and coming apart, or the wire nut isn't holding the wires very well. Sometimes I can't find the problem, but have been able to use LED light bulbs until somebody smarter then I am can figure out where the problem is.

 

[KYErik]

Thanks guys! The projector is at my parents' house. We are planning to watch some old home movies after the big meal on Thursday. I will let you know how it worked out.

 

[vvanders]

Those "long life bulbs" are exactly the ones the EPA has banned for being so "inefficient" . Considered energy wasters as they turn most of the consumed electricity into heat instead of light.
Thanks to that attitude we now have those wonderful CFLs and the ghastly light of LEDs.
Progress!

They've made pretty big strides in LED color temperature lately. Incandescents are pretty inefficient, just look at the huge changes in flashlights over the last 5 years.

 

[KYErik]

From:
Watts/Volts/Amps/Ohms conversion calculator

My guess is this....

The original 30v 80w bulb would be about 11.25 ohms resistance and pull about 2.6666 amps.


Go to that link and plug in some numbers. Its kind of fun.

Thanks for the link to that calculator. Based on what everyone has been saying- that the resistance/ohms are what was most important for making the same amount of light- I used the calculator to find that a 12 volt bulb of 12.8 watts would have about 11.25 ohms of resistance. I went ahead and bought a pack of 12 volt 10 watt halogen bulbs at Menard's- should give about 62.5 watts. Just $8 for a 5 pack of bulbs. I will solder one in and give it a try after I try the 120 volt 250 watt bulb.

 

[k0ua]

Thanks for the link to that calculator. Based on what everyone has been saying- that the resistance/ohms are what was most important for making the same amount of light- I used the calculator to find that a 12 volt bulb of 12.8 watts would have about 11.25 ohms of resistance. I went ahead and bought a pack of 12 volt 10 watt halogen bulbs at Menard's- should give about 62.5 watts. Just $8 for a 5 pack of bulbs. I will solder one in and give it a try after I try the 120 volt 250 watt bulb.

It will be interesting to see what burns out first the fuse protecting the 30 volt power supply or the filament of the lamp rated for 12 volts now operating on 30 volts. The bulb should light up nice and bright for a very short time.. It may seem a lot like like a flashbulb or it may work for a while, or it may pop the power supply in the projector. It will be an interesting experiment. Please report back.

 

[bcp]

I'm betting the bulb won't fit the socket.

Bruce

 

[KYErik]

By now you all know that I know very little about bulbs/voltage/resistance. So this bulb could overwhelm the projector power supply? If it has a resistance rating of 14.4 ohms and the factory bulb has a resistance of 11.25 ohms, wouldn't it draw less current than the factory bulb?